A comparative genome analysis of the () class .

is recognized for its ability to anaerobically ferment dichloromethane (DCM), and a catabolic model has recently been proposed. is currently the only axenic representative of its class, the , according to the Genome Taxonomy Database. However, substantial additional diversity has been revealed in this lineage through culture-independent exploration of anoxic habitats. Here we performed a comparative analysis of 10 members of the representing three orders, and infer that anaerobic DCM degradation appears to be a recently acquired trait only present in some members of the order . Inferred traits common to the class include the use of amino acids as carbon and energy sources for growth, energy generation via a remarkable range of putative electron-bifurcating protein complexes and the presence of S-layers. The ability of to grow on serine without DCM was experimentally confirmed and a high abundance of the electron-bifurcating protein complexes and S-layer proteins was noted when this organism was grown on DCM. We suggest that members of the are low-abundance fermentative scavengers in anoxic habitats.